query GetPersons {
  persons {
    __typename
    id
    name
    age
    ... on Student {
      universityName
    }
    ... on Employee {
      companyName
    }
  }
}

mutation AddStudent {
  addStudent(
    input: { name: "Student 1", dateOfBirth: "1991-11-30T00:00:00.000Z", universityName: "Uni 1" }
  ) {
    id
    age
  }
}

mutation AddEmployee {
  addEmployee(
    input: { name: "Employee 1", dateOfBirth: "1995-07-23T00:00:00.000Z", companyName: "Company 1" }
  ) {
    id
    age
  }
}
